System for decomposing organic compound

ABSTRACT

A system for decomposing a liquid or gaseous organic compound comprises a ultraviolet decomposition unit and an intermediate product treatment apparatus. The ultraviolet decomposition unit decomposes an organic compound contained in polluted liquid or polluted gas by irradiating ultraviolet rays whose wavelength is less than 300 nm to the polluted liquid or the polluted gas containing the organic compound. An acid electrolytic water feed pipe and an alkali electrolytic water feed pipe are respectively connected to the intermediate product treatment apparatus through valves to neutralize an intermediate product, which results from decomposition of the organic compound, for decomposition by selectively adding strong alkali electrolytic water and strong acid electrolytic water to the polluted liquid or the polluted gas containing the intermediate product.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system for decomposing a gaseous or liquidorganic compound.

2. Description of the Prior Art

Organic compounds such as trichloroethylene and tetrachloroethylene havebeen used over a long term of years as detergents and solvents in thefield related to semiconductors as well as the field of metal oilcleaning, dry cleaning and the like because of their high solvency.

However, it has been recently ascertained that carcinogen is containedin these chlorine organic compounds, so that their harmfulnessconstitutes a social problem, resulting in enforcement of regulation onemission of the chlorine organic compounds. For this reason, in placesof industries that have emitted a large quantity of chlorine organiccompounds after use in the past, pollution of the soil, as well aspollution of the ground water, within the sites and the peripheriesthereof is at serious issue.

In addition, polluted gas containing a certain kind of organic compoundemits an offensive odor, which sometimes causes environmentaldeterioration.

To purify the ground water, there has been normally the need forregeneration of an organic compound by pumping up polluted ground waterwith a storage pump and then removing the organic compound contained inthe pumped-up ground water by adsorption with activated carbon, oralternatively, separating the organic compound contained in the pollutedground water by adsorption with the activated carbon or the like afterseparating the organic compound as exhaust gas with the aerationequipment. For this reason, the large-scaled adsorption equipment usingthe activated carbon is required for places that are polluted in highconcentration over a wide area, so that a burden on the facility cost,as well as the running cost, constitutes a problem.

In addition, to purify the soil, there has been the need forregeneration of an organic compound by drawing soil gas by suction andthen removing the organic compound contained in the soil gas byadsorption with activated carbon. For this reason, the large-scaledadsorption equipment using the activated carbon is also required forplaces that are polluted in high concentration over a wide area, so thata burden on the facility cost, as well as the running cost, constitutesa problem.

If making an attempt to remove the organic compound contained in thesoil gas by adsorption solely with the activated carbon, the activatedcarbon needs to be exchanged frequently, and besides, a tremendouslabor, as well as an enormous expense, is required for exchange andregeneration of the activated carbon, disposal of the wasted activatedcarbon and the like, resulting in a remarkable increase in burden onenterprises to realize purification of the soil.

On the other hand, a technique for decomposing an organic compound byultraviolet irradiation is well known. For surface cleaning of asemiconductor wafer, for instance, an Excimer lamp and the like are usedfor irradiation of high energy ultraviolet rays (whose wavelength is 172nm) to decompose the organic compound on the wafer surface. Irradiationof high-energy ultraviolet rays as described above results indecomposition of the organic compound in an extremely short period oftime. However, the Excimer lamp is exceptionally expensive and needs notonly the enormous facility cost but also the extremely high powerconsumption, so that it is supposed that the Excimer lamp is not suitedto be of practical use for purification of the soil.

In addition, if making an attempt to decompose the organic compound byultraviolet irradiation with a low pressure mercury lamp, a middlepressure mercury lamp and high pressure mercury lamp that are availableat low cost, an unstably reactive substance such as hydrogen chlorideand halacetic acid is produced as an intermediate product, and as aresult, it takes much time to decompose the intermediate product into upto stable substances.

In this connection, in Japanese Patent Application Laid-open No.8-24335, there is disclosed a method for decomposing an organic chlorinecompound by steps of decomposing the organic chlorine compound into upto a reaction intermediate having chlorine atoms by irradiatingultraviolet rays inclusive of ultraviolet rays whose wavelength is notmore than 300 nm to gas containing the organic chlorine compound, andfurther decomposing the reaction intermediate through the biologicaltreatment.

The biological treatment has the advantage of adaptability to theenvironment, whereas it presents problems such as a difficulty inmanaging the treatment and a need for much time to conduct the treatmentdue to the extremely slow proceeding of decomposition. In particular, itis supposed that the biological treatment is not enough to cope withhigh concentration pollution.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system fordecomposing a liquid or gaseous organic compound, and more specifically,a decomposing system which may decompose polluted liquid or polluted gascontaining an organic compound efficiently in a short period of time, iseasy to treat an intermediate product resulting from ultravioletdecomposition. of the organic compound, and permits miniaturization of apurifying apparatus used for the final waste water treatment so thatthere is less facility cost required, as well as less running costrequired.

A system for decomposing an organic compound according to the presentinvention comprises a ultraviolet decomposition unit that decomposes anorganic compound contained in polluted liquid or polluted gas byirradiating ultraviolet rays whose wavelength is less than 300 nm to thepolluted liquid or polluted gas containing the organic compound, and anintermediate product treatment apparatus that is connected to an acidelectrolytic water feed pipe and an alkali electrolytic water feed pipethrough valves and neutralizes an intermediate product, which resultsfrom decomposition of the organic compound, for decomposition byselectively adding strong alkali electrolytic water or strong acidelectrolytic water to the intermediate product or the polluted liquidcontaining the intermediate product.

It is supposed that the organic compound contained in the pollutedliquid or the polluted gas is decomposed as the result of segmentationof its chemical bond by ultraviolet irradiation, while the intermediateproducts resulting from decomposition of the organic compound are placedin the form of admixture in an unstable radical state by ultravioletirradiation. These unstable intermediate products are neutralized ordecomposed in touch with the strong alkali electrolytic water or thestrong acid electrolytic water, and as a result, may be transformed intomore stable harmless substances. In addition, the strong alkalielectrolytic water or the strong acid electrolytic water added orsprayed to the polluted liquid or the polluted gas is harmless to thehuman body, and therefore, is not in danger of environmental pollution.

It does not matter if the intermediate product treatment apparatus isconnected to the downstream side of the ultraviolet decomposition unitto selectively add the strong alkali electrolytic water and the strongacid electrolytic water to the polluted liquid or the polluted gashaving passed through the ultraviolet decomposition unit, oralternatively, the intermediate product treatment apparatus is connectedto an intermediate portion of the ultraviolet decomposition unit toselectively add or spray the strong alkali electrolytic water and thestrong acid electrolytic water to the polluted liquid or the pollutedgas within the ultraviolet decomposition unit.

There are some cases where the strong alkali electrolytic water and/orthe strong acid electrolytic water are or is added to the pollutedliquid on the upstream side of the ultraviolet decomposition unit. Inaddition, when the intermediate product treatment apparatus is connectedto the downstream side of the ultraviolet decomposition unit, there arealso some cases where the strong alkali electrolytic water and/or strongacid electrolytic water are or is sprayed to the polluted gas within theultraviolet decomposition unit.

Use of the above configuration may accelerate decomposition of theorganic compound by ultraviolet irradiation, and as a result, may reducea time taken for the treatment. The strong alkali electrolytic water andthe strong acid electrolytic water that are added into the ultravioletdecomposition unit are produced at the same time with the strong alkalielectrolytic water and the strong acid electrolytic water that aresprayed in the intermediate product treatment apparatus, and as aresult, it is possible to hold down an increase in cost.

The ultraviolet decomposition unit may be made up of a reaction vesselhaving a plurality of ultraviolet lamps set up around a transparent tubethat allows the polluted liquid to pass, and reflectors respectivelyarranged behind the ultraviolet lamps. Accordingly, the ultraviolet raysare irradiated from the plurality of ultraviolet lamps to the pollutedliquid, and as a result, the decomposition performance is improved.

There are also some cases where the ultraviolet decomposition unit ismade up of a decomposition cell having a ultraviolet lamp arrangedtherein, and a gas inlet is formed in a peripheral wall of thedecomposition cell to allow the polluted gas to blow along a diameter ofthe decomposition cell. With this arrangement, transfer of the pollutedgas along an inner surface of the decomposition cell hardly occurs, andas a result, the polluted gas may stay in the decomposition cell for alonger period of time, while the decomposition performance is improvedwith the increasing intensity of ultraviolet irradiation.

Incidentally, a low pressure mercury lamp, a middle pressure mercurylamp, a high pressure mercury lamp, an amalgam lamp, a halogen lamp, anExcimer lamp and the like are available for the ultraviolet lamp.

Use of a plurality of reaction vessels connected in series permits areduction in concentration as the result of efficient decomposition ofthe organic compound inclusive of high-concentration organic compound.On the other hand, use of the plurality of reaction vessels connected inparallel permits an increase in amount of polluted liquid or pollutedgas to be treated.

It is preferable to hang down the plurality of ultraviolet lamps atequal intervals from an upper surface of the decomposition cell so as torealize uniform ultraviolet irradiation to the polluted gas. Since theultraviolet intensity is inversely proportional to the irradiationdistance, the distance between the ultraviolet lamps is limited to 100mm or less, preferably, 20 mm or less.

Since both of the transparent tube that allows the polluted liquid topass and a protection tube of the ultraviolet lamp need to preventultraviolet rays of relatively short - wavelength from being attenuated,it is preferable to use synthetic quartz glass, which permitstransmission of 80% or more of ultraviolet rays whose length is not lessthan 172 nm, as a material of the above tubes.

According to the system for decomposing the organic compound accordingto the present invention, the harmful organic compound contained in thepolluted liquid or the polluted gas is decomposed by irradiation ofrelatively high energy ultraviolet rays whose wavelength is less than300 nm, and the unstable intermediate product resulting fromdecomposition of the organic compound is also decomposed byneutralization with the strong alkali electrolytic water and the strongacid electrolytic water, so that there is less treatment time required,while the need for so much large-scaled apparatus is eliminated.

In addition, some organic compounds that are not completely decomposedby ultraviolet irradiation may be also decomposed up to a lower level byaddition of the strong alkali electrolytic water and the strong acidelectrolytic water.

Furthermore, the strong alkali electrolytic water and the strong acidelectrolytic water used for neutralization of the intermediate productare harmless to the human body, and therefore, are not in danger ofenvironmental pollution.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and features of the invention willbecome apparent from the following description of preferred embodimentsof the invention with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram showing an embodiment of a system fordecomposing a liquid organic compound according to the presentinvention;

FIG. 2 is a sectional view showing a reaction vessel for use in thedecomposing system of FIG. 1;

FIG. 3 is a schematic view showing a test apparatus used for tests 1 to5;

FIGS. 4A-and 4B show the result of measurement on the concentration ofTCE (trichloroethylene) according to the test 1;

FIGS. 5A and 5B show the result of measurement on the concentration of1, 1-DCE (dichloroethane) according to the test 2;

FIGS. 6A and 6B show the result of measurement on the concentration oftrans-1, 2-DCE according to the test 3;

FIGS. 7A and 7B show the result of measurement on the concentration ofcis-1, 2-DCE according to the test 4;

FIG. 8 shows the result of measurement on the concentrations of 1,1-DCE,trans-1,2-DCE, cis-1,2-DCE, TCE and PCE (tetrachloroethylene) accordingto the test 5;

FIG. 9 shows the result of measurement on the concentration of TCEtogether with the decomposition rate of TCE according to the test 6;

FIG. 10 shows the result of measurement on the concentration of TCEaccording to the test 7;

FIG. 11 shows the result of calculation on the decomposition rate of TCEaccording to the test 7;

FIG. 12 is a schematic view showing a test apparatus used for the test8;

FIG. 13 shows a change of the concentration of TCE and that of thedecomposition rate of TCE in a case where a flow rate was decreasedgradually according to the test 8;

FIG. 14 shows a change of the concentration of TCE and that of thedecomposition rate of TCE in a case where a flow rate was increasedgradually according to the test 8;

FIG. 15 is a schematic view showing a test apparatus used for the test9;

FIG. 16 shows the concentration of TCE and the decomposition rate of TCEas the result of the test 9 under the conditions 1;

FIG. 17 shows the concentration of TCE and the decomposition rate of TCEas the result of the test 9 under the conditions 2;

FIG. 18 shows the concentration of TCE and the decomposition rate of TCEas the result of the test 9 under the conditions 3;

FIG. 19 shows the concentration of TCE and the decomposition rate of TCEas the result of the test 9 under the conditions 4;

FIG. 20 is a block diagram showing an embodiment of a system fordecomposing a gaseous organic compound according to the presentinvention;

FIG. 21 is a side sectional view showing a decomposition cell for use inthe decomposing system of FIG. 20;

FIG. 22 is a plan sectional view showing the decomposition cell of FIG.21;

FIG. 23 shows the result of measurement on the pollution concentrationaccording to the test 10;

FIG. 24 shows the result of measurement on a pH value according to thetest 10;

FIG. 25 shows the result of measurement on the pollution concentrationaccording to the test 11;

FIG. 26 shows the result of measurement on a pH value according to thetest 11;

FIG. 27 shows a change of the concentration of an organic compound withthe passage of time according to the test 12;

FIG. 28 shows a change of the concentration of an intermediate productwith the passage of time according to the test 12;

FIG. 29 shows a change of the concentration of an organic compound withthe passage of time according to the test 13;

FIG. 30 shows a change of the concentration of an intermediate productwith the passage of time according to the test 13;

FIG. 31 shows a change of the concentration of an organic compound withthe passage of time according to the test 14;

FIG. 32 shows a change of the concentration of an intermediate productwith the passage of time according to the test 14;

FIG. 33 shows a change of the concentration of organic compound with thepassage of time according to the test 15;

FIG. 34 shows a change of the concentration of an intermediate productwith the passage of time according to the test 15;

FIG. 35 shows a change of the concentration of an organic compound withthe passage of time according to the test 16;

FIG. 36 shows a change of the concentration of an intermediate productwith the passage of time according to the test 16;

FIG. 37 shows a change of the concentration of an organic compound withthe passage of time according to the test 17;

FIG. 38 shows a change of the concentration of an intermediate productwith the passage of time according to the test 17;

FIG. 39 shows a change of the concentration of an organic compound withthe passage of time according to the test 18;

FIG. 40 shows a change of the concentration of an intermediate productwith the passage of time according to the test 18;

FIG. 41 is a schematic view showing a test apparatus used for tests 19to 24;

FIG. 42 shows the result of measurement on the concentration of TCEaccording to the test 19;

FIG. 43 shows the result of calculation on the decomposition rate of TCEaccording to the test 19;

FIG. 44 shows the result of measurement on the concentration of PCEaccording to the test 20;

FIG. 45 shows the result of calculation on the decomposition rate of PCEaccording to the test 20;

FIG. 46 shows the result of measurement on the concentration of cis-1,2-DCE according to the test 21;

FIG. 47 shows the result of calculation on the decomposition rate ofcis-1, 2-DCE according to the test 21;

FIG. 48 shows the result of measurement on the concentration ofmonochlorobenzene according to the test 22;

FIG. 49 shows the result of calculation on the decomposition rate ofmonochlorobenzene according to the test 22;

FIG. 50 shows the result of measurement on the concentration of ethylacetate according to the test 23;

FIG. 51 shows the result of calculation on the decomposition rate ofethyl acetate according to the test 23;

FIG. 52 shows the result of measurement on the concentration of tolueneaccording to the test 24;

FIG. 53 is a schematic view showing a test apparatus used for the test25;

FIG. 54 shows the concentration of TCE as the result of measurementaccording to the test 25, together with the decomposition rate of TCE;

FIG. 55 is a side sectional view showing a test cell used for the test26;

FIG. 56 is a plan sectional view showing the test cell used for the test26;

FIG. 57 shows the decomposition rate of TCE according to the test 26;

FIG. 58 is a schematic view showing a test apparatus used for tests 27to 29;

FIGS. 59A and 59B show a change of the concentration of TCE with thepassage of time according to the test 27;

FIGS. 60A and 60B show a change of the concentration of PCE with thepassage of time according to the test 28;

FIGS. 61A and 61B show a change of the concentration of cis-1, 2-DCEwith the passage of time according to the test 29; and

FIG. 62 shows a change of the concentration of CMMS(chloromethylmethylsulfide) according to the test 30.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Firstly, a system for decomposing a liquid organic compound according tothe present invention will be described with reference to FIGS. 1 to 19.

The system for decomposing the liquid organic compound is connected to apumping apparatus (not shown) for pumping up polluted liquid containingan organic compound from the polluted soil and, as shown in FIG. 1,comprises an electrolytic water adding tank 1, into which the pollutedliquid is introduced from the pumping apparatus, a ultravioletdecomposition unit 2 connected to the downstream side of theelectrolytic water adding tank 1, an intermediate product treatmentapparatus 3 connected to the downstream side of the ultravioletdecomposition unit 2, an activated carbon adsorption unit 4 connected tothe downstream side of the intermediate product treatment apparatus 3and an electrolytic water producing apparatus 5.

“Oxylizer Medica CL” (a trade name) manufactured by MIURA DENSHI INC isavailable for the electrolytic water producing apparatus 5. When watercontaining water soluble electrolyte such as sodium chloride, potassiumchloride and magnesium chloride is electrolyzed by the electrolyticwater producing apparatus 5, strong acid electrolytic water is producedfrom the anode side, while strong alkali electrolytic water is producedfrom the cathode side.

The strong acid electrolytic water and the strong alkali electrolyticwater obtained in this manner are harmless to the human body andtherefore, are not in danger of environmental pollution even if beingbrought into touch with the polluted liquid as functional water.

The anode side of the electrolytic water producing apparatus 5 and theelectrolytic water adding tank 1 are connected together through an acidelectrolytic water feed pipe 6 such that the strong acid electrolyticwater is added to the polluted liquid within the electrolytic wateradding tank 1 by opening a valve (not shown) set up at a portion ofconnection between the electrolytic water adding tank 1 and the acidelectrolytic water feed pipe 6.

In addition, the cathode side of the electrolytic water producingapparatus 5 and the electrolytic water adding tank 1 are connectedtogether through an alkali electrolytic water feed pipe 7 such that thestrong alkali electrolytic water is added to the polluted liquid withinthe electrolytic water adding tank 1 by opening a valve (not shown) setup at a portion of connection between the electrolytic water adding tank1 and the alkali electrolytic water feed pipe 7.

The ultraviolet decomposition unit 2 is composed of two reaction vessels11 connected in series. As shown in FIG. 2, each reaction vessel 11 hasa transparent tube 8 arranged in the center of a light-shielding case 14and connected to the electrolytic water adding tank 1, four ultravioletlamps 9 set up around the transparent tube at equal intervals and areflector 10 arranged behind each ultraviolet lamp 9.

The transparent tube 8 is made of a material such as synthetic quartzglass that permits transmission of 80% or more of ultraviolet rays whosewavelength is not less than 172 nm such that the polluted liquid withthe strong acid electrolytic water and/or the strong alkali electrolyticwater added in the electrolytic water adding tank 1 may pass through theinside of the transparent tube.

While a low pressure mercury lamp and the like for irradiation ofultraviolet rays whose wavelength is less than 300 nm are available forthe ultraviolet lamp 9, it is to be understood that use of ultravioletrays whose wavelength is limited to 254 nm or less, preferably, 185 nmprovides the increased decomposition performance for the organiccompound.

An upper part and a lower part of the intermediate product treatmentapparatus 3 are connected through a circulation pipe 13 having a pump12. For this reason, the polluted liquid having flowed into theintermediate product treatment apparatus 3 through the ultravioletdecomposition unit 2 is sent to the upper part of the intermediateproduct treatment apparatus 3 for circulation in the intermediateproduct treatment apparatus 3 after being forced upward through thecirculation pipe 13 with the pump 12.

In addition, the intermediate product treatment apparatus 3 is equippedwith a pH meter 23, wherein a pH value of the polluted liquid havingflowed into the intermediate product treatment apparatus 3 may bemeasured.

Furthermore, the alkali electrolytic water feed pipe 7 and the acidelectrolytic water feed pipe 6 are respectively connected to thecirculation pipe 13 through valves (not shown) such that the strongalkali electrolytic water and the strong acid electrolytic water areselectively added to the circulating polluted liquid in the intermediateproduct treatment apparatus 3 by opening the valves according to the pHvalue of the polluted liquid by measurement with the pH meter 23.

An activated carbon filter is incorporated in the activated carbonadsorption unit 4, wherein a small quantity of organic compound stillremaining in the liquid having passed through the intermediate producttreatment apparatus. 3 is removed by adsorption.

In addition, a drainage pipe 17 having a pump 16 is connected to theactivated carbon adsorption unit 4, so that clean liquid having passedthrough the activated carbon filter is drained to the outside throughthe drainage pipe.

The system for decomposing the organic compound is applied as follows.

The polluted liquid containing the organic compound is introduced intothe electrolytic water adding tank 1 after being pumped up from thepolluted soil, and the strong acid electrolytic water and/or the strongacid alkali electrolytic water produced by the electrolytic producingapparatus 5 are or is added to the polluted liquid within theelectrolytic water adding tank 1.

The polluted liquid with the electrolytic water added in theelectrolytic water adding tank 1 passes successively through thetransparent tube 8 of each of two reaction vessels 11 that constitutethe ultraviolet decomposition unit 2. The ultraviolet lamps 9 set uparound the transparent tube 8 continue to irradiate the ultraviolet raysto the polluted liquid within the transparent tube 8 during the passageof the polluted liquid through the transparent tube.

Then, the organic compound contained in the polluted liquid isdecomposed by ultraviolet irradiation. Besides, the reaction ofdecomposition of the polluted liquid is accelerated in the presence ofthe strong acid electrolytic water and/or the strong alkali electrolyticwater.

The intermediate product resulting from decomposition of the organiccompound is contained in the polluted liquid having passed through theultraviolet decomposition unit 2, so that the polluted liquid that flowsinto the intermediate product treatment apparatus 3 is supposed to bethe polluted liquid containing the intermediate product.

The polluted liquid having flowed into the intermediate producttreatment apparatus 3 circulates in the intermediate product treatmentapparatus 3 through the circulation pipe 13 for a certain period oftime, while the pH value of the polluted liquid is measured with the pHmeter 23. On the occasion of passage of the polluted liquid through thecirculation pipe 13, the strong alkali electrolytic water or the strongacid electrolytic water is added to the polluted liquid according to themeasured pH value, and as a result, the intermediate product containedin the polluted liquid is neutralized.

It is a matter of course that the polluted liquid containing theintermediate product sometimes shows neutrality depending on the kin oforganic compounds contained in the polluted liquid. In this case, thestrong alkali electrolytic water and the strong acid electrolytic waterare simultaneously added to the polluted liquid for decomposition of theintermediate product.

In addition, a small quantity of organic compound still remaining in theliquid having passed through the ultraviolet decomposition unit 2 isalso further decomposed by addition of the strong alkali electrolyticwater and the strong acid electrolytic water. The liquid havingcirculated in the intermediate product treatment apparatus 3 for acertain period of time flows into the activated carbon adsorption unit 4and is then drained to the outside after the intermediate product andthe organic compound that still remain in small quantity are removed byadsorption with the activated carbon filter.

Incidentally, as shown by broken lines in FIG. 1, the ultravioletdecomposition unit 2 may be also used as the intermediate producttreatment apparatus by connecting the acid electrolytic water feed pipe6 and the alkali electrolytic water feed pipe 7 also to the reactionvessels 11 through the valves.

In this case, each reaction vessel 11 is equipped with the pH meter 23.Thus, the strong acid electrolytic water and the strong alkalielectrolytic water are selectively added to the polluted liquid withinthe reaction vessels 11 by opening or closing the valves according tothe measured pH value of the polluted liquid, and as a result, theintermediate product is neutralized for decomposition. In addition, thestrong acid electrolytic water and the strong alkali electrolytic wateradded to the polluted liquid for the treatment of the intermediateproduct are supposed to be also applied to decomposition of the organiccompound contained in the polluted liquid.

In this place, the intermediate product treatment apparatus 3 may be ormay not be installed on the downstream side of the ultravioletdecomposition unit 2.

In addition, it does not matter if the strong alkali electrolytic wateror the strong acid electrolytic water is added to the polluted liquidwithin the intermediate product treatment apparatus 3 after the organiccompound contained in the polluted liquid within the ultravioletdecomposition unit 2 is decomposed solely by ultraviolet irradiationwithout installing the electrolytic water adding tank 1 on the upstreamside of the ultraviolet decomposition unit 2.

Furthermore, it is also possible to use an ultraviolet decompositionunit having a plurality of ultraviolet lamps set up in a water tank thatreserves the polluted liquid.

A description of examples will now be given as follows.

The test 1 was conducted in the following manner: 500 ml of the pollutedliquid containing trichloroethylene (hereinafter referred to as TCE)with the concentration of 7 mg/l was poured in the glass bottle 18, asshown in FIG. 8, and 5% amount of strong acid electrolytic water ordistilled water was added. Then, a change of the concentration of TCEwas observed for 20 minutes for one case in which the ultraviolet lamp9, protected by a quartz tube 19, which irradiates ultraviolet rays of254 nm wavelength, was arranged in the glass bottle 18, and for anothercase in which the ultraviolet lamp 9, protected by a quartz tube 19,which irradiates ultraviolet rays of 185nm wavelength, was arranged inthe glass bottle 18.

FIGS. 4A and 4B shows the change of the concentration of TCE in eachtest sample.

The test 2 was conducted in the same manner as the test 1, except that1,1-dichloroethane (hereinafter referred to as 1,1-DCE) was used,instead of TCE. FIGS. 5A and 5B show the result of measurement on theconcentration of 1,1-DCE.

The test 3 was conducted in the same manner as the test 1, except thattrans-1, 2-dichloroethane (hereinafter referred to as trans-1, 2-DCE)was used, instead of TCE. FIGS. 6A and 6B show the result of measurementon the concentration of trans-1,2-DCE.

The test 4 was conducted in the same manner as the test 1, except thatcis-1,2-dichloroethane (which will be hereinafter referred to ascis-1,2-DCE) was used, instead of TCE. FIGS. 7A and 7B show the resultof measurement on the concentration of cis-1,2-DCE.

The tests 1 to 4 have proven that the organic compound is decomposed byultraviolet irradiation and as a result, causes a reduction inconcentration, and in particular, the decomposition performance isimproved with the strong acid electrolytic water added when theultraviolet rays of longer wavelength are in use.

The test 5 was conducted in the following manner: 500 ml of the pollutedliquid containing 1,1 -DCE with the concentration of 14.2 mg/l, 500 mlof the polluted liquid containing trans-1,2-DCE with the concentrationof 16.5 mg/l, 500 ml of the polluted liquid containing cis-1,2-DCE withthe concentration of 14.2 mg/l, 500 ml of the polluted liquid containingTCE with the concentration of 10.8 mg/l and 500 ml of the pollutedliquid containing tetrachloroethylene (hereinafter referred to as PCE)with the concentration of 9.8 mg/l, were poured respectively in the testapparatus similar to that used in the test 1, and further 5% amount ofstrong acid electrolytic water was added. Then, the concentration afterthe lapse of 20 minutes was examined, respectively, for one case inwhich ultraviolet rays of 254 nm wavelength was irradiated and anothercase in which ultraviolet rays of 185 nm wavelength was irradiated. FIG.8 shows the result of measurement on the concentrations.

The test 5 has proven that the organic compound having a larger numberof chlorine atoms is more likely to be decomposed.

The test 6 was conducted by collecting in a quartz test tube 8 ml of thepolluted liquid containing TCE, with 5% amount of strong acidelectrolytic water, which is 2.53 in pH value, 0.236 mS/m inconductivity and 1046 mV in oxidation reduction potential, added. Andthen the concentration of TCE before and after ultraviolet irradiationwas measured and also the decomposition rate of TCE was found for onecase in which a germicidal lamp was used for irradiation of ultravioletrays whose wavelength is as short as less than 300 nm and for anothercase in which a Black Light as disclosed in Japanese Patent ApplicationLaid-open No. 2001-170666 was used for irradiation of ultraviolet rayswhose wavelength is as long as 300 nm or more. FIG. 9 shows the resultof measurement on the concentration of TCE, together with thedecomposition rate of TCE. Measurement on the concentration of TCE wasconducted using a gas chromatograph after extraction of hexane.

The test 6 has proven that irradiation of ultraviolet rays whosewavelength is as short as less than 300 nm provides extremely higherdecomposition performance than that in a case of irradiation ofultraviolet rays whose wavelength is as long as 300 nm or more. It hasalso proven that irradiation of ultraviolet rays whose wavelength is asshort as less than 300 nm for 5 minutes results in a decomposition ratethree times as much as that in a case of irradiation of ultraviolet rayswhose wavelength is as long as 300 nm or more.

The test 7 was conducted in the same manner as the test 6 to measure theconcentration of TCE and also to find the decomposition rate of TCE byirradiating the ultraviolet rays for 30 seconds from the germicidal lampto the TCE polluted liquid put in the quartz test tube to change theconcentration of the strong acid electrolytic water to 1, 3, 5 and 10%,while changing the light intensity to 1.0, 0.4 and 0.2 mW/cm² byadjusting the distance between the quartz test tube and the germicidallamp. FIG. 10 shows the concentration of TCE, and FIG. 11 shows thedecomposition rate of TCE.

The test 7 has proven that the strong acid electrolytic water with theconcentration of 5% provides the highest decomposition rate, and thereis almost no effect on the decomposition performance even after theconcentration of the strong acid electrolytic water exceeds 5%.

FIG. 12 a test apparatus used for the test 8. The test apparatus usedherein has the reaction vessel 11 connected to the downstream side of awater tank 20 through the pump 21 and a flow meter 22. The reactionvessel 11 is composed of the quartz transparent tube 8 whose innerdiameter is 32 mm, the ultraviolet lamps 9 made up of the germicidallamps and the reflectors 10 arranged on the opposite sides of the quartztransparent tube 8, as shown in FIG. 2. By reserving in the water tank20 the polluted liquid containing TCE with the concentration of 0.3mg/l, with 5% amount of strong acid electrolytic water, which is 2.53 inpH value, 0.236 mS/m in conductivity and 1046 mV in oxidation reductionpotential, added, the concentration of TCE was measured by changing aflow rate of the liquid to be treated and then the decomposition rate ofTCE was found.

FIG. 13 shows the result of measurement when the flow rate was decreasedfrom 8 l/min to 1 l/min, and FIG. 14 shows the result of measurementwhen the flow rate was increased from 2 l/min to 8 l/min.

The test 8 has proven that the decomposition rate is increased with thedecreasing flow rate, and as a result, use of a large number of reactionvessels connected in parallel for flowing the small amount of pollutedliquid to each reaction vessel will be enough to increase the amount ofliquid to be treated without degrading the decomposition performance.

FIG. 15 shows a test apparatus used for the test 9. The test apparatusused herein has a first reaction vessel 11 a and a second reactionvessel 11 b that are connected in series through the pump 21 on thedownstream side of the water tank 20. Each of the reaction vessels 11 aand 11 b is composed of the quartz glass tube 8 whose inner diameter is10.5 mm and effective length is 60 cm, four ultraviolet lamps 9constituting 20 W germicidal lamps and four reflectors 10 arrangedaround the quartz glass tube 8, as shown in FIG. 2. The polluted liquidcontaining TCE, with 5% amount of strong acid electrolytic water, whichis 2.53 in pH value, 0.236 mS/m in conductivity and 1046 mV in oxidationreduction potential, added, is reserved in the water tank 20.

Then, the test 9 was conducted to measure the concentration of TCE onthe drainage side and also to find the decomposition rate of TCE at thetime when all the ultraviolet lamps 9 were turned off, the time whensolely the ultraviolet lamps 9 of the first reaction vessel 11 a werelighted, the time when solely the ultraviolet lamps 9 of the secondreaction vessel 11 b were lighted, and the time when the ultravioletlamps 9 of the first and second reaction vessels 11 a and 11 b werelighted for a first case where the polluted liquid containing TCE withthe concentration of 0.05 mg/l was caused to flow at a flow rate of 800ml/min, for a second case where the polluted liquid containing TCE withthe concentration of 0.03 mg/l was caused to flow at a flow rate of 1000ml/min, for a third case where the polluted liquid containing TCE withthe concentration of 0.3 mg/l was caused to flow at a flow rate of 1000ml/min and for a fourth case where the polluted liquid containing TCEwith the concentration of 3.0 mg/l was caused to flow at a flow rate of1000 ml/min. FIG. 16 shows the concentration of TCE and thedecomposition rate of TCE as the result of the test 9 for the firstcase, FIG. 17 shows those as the result of the test 9 for the secondcase, FIG. 18 shows those as the result of the test 9 for the thirdcase, and FIG. 19 shows those as the result of the test 9 for the fourthcase.

Incidentally, “a theoretical value” shown in FIGS. 16 to 18 is the valueobtained by calculating the decomposition rate of TCE in the firstreaction vessel 11 a and that of TCE in the second reaction vessel 11 b,individually, and then calculating the decomposition rate of TCE afterthe passage through both the reaction vessels 11 a and 11 b using thedecomposition rates individually obtained.

The test 9 has proven that use of a plurality of reaction vessels 11connected in series increases the decomposition rate of the organiccompound, and its value sufficiently agrees with the theoretical value.In addition, it has also proven that the decomposition performance isincreased with the increases of concentration of the organic compound.

A description will now be given of a system for decomposing a gaseousorganic compound according to the present invention with reference toFIGS. 20 to 62.

The system for decomposing the gaseous organic compound is connected toa gas suction apparatus for drawing polluted gas containing the organiccompound by suction from the polluted soil and, as shown in FIG. 20,comprises a ultraviolet decomposition unit 31, into which the pollutedgas is introduced, an intermediate product treatment apparatus made upof a scrubber 32 connected to the downstream side of the ultravioletdecomposition unit 31, an activated carbon adsorption unit 33 connectedto the downstream side of the scrubber 32 and an electrolytic waterproducing apparatus 34. “Oxylizer Medica CL” (a trade name) manufacturedby MIURA DENSHI INC is available for the electrolytic water producingapparatus 34. When water containing water soluble electrolyte such assodium chloride, potassium chloride and magnesium chloride iselectrolyzed by the electrolytic water producing apparatus 34, strongacid electrolytic water is produced from the anode side, while strongalkali electrolytic water is produced from the cathode side.

The strong acid electrolytic water and the strong alkali electrolyticwater obtained in this manner are harmless to the human body, andtherefore, are not in danger of environmental pollution even if beingbrought into touch with the polluted gas as functional water.

The ultraviolet decomposition unit 31 is composed of two decompositioncells 36, connected in series, arranged inside a stainless steel pipe,and each decomposition cell 36 has a plurality of ultraviolet lamps madeup of low pressure mercury lamps 35 (See FIGS. 21 and 22).

Each low pressure mercury lamp 35 is a lamp having a protection tubemade of a material such as synthetic quartz glass that permitstransmission of 80% or more of ultraviolet rays whose wavelength is 172nm or more, and irradiates ultraviolet rays whose power consumption is13 W. and wavelengths are 254 nm and 185 nm.

In addition, as shown in FIG. 21, the low pressure mercury lamps 35 arehung down from the upper surface of each decomposition cell 36 such thatone lamp is placed in the center of the upper surface of eachdecomposition cell 36, while others are placed at equal intervals alongthe peripheral edge of the upper surface: thereof.

As shown in FIG. 22, the polluted gas is introduced through a gas inlet37 formed at one diametric end in an upper part of the peripheral wallof one decomposition cell 36, while being extracted through a gas outlet38 formed at one diametric end in an upper part of the peripheral wallof the other decomposition cell 36.

Then, the anode side of the electrolytic water producing apparatus 34and each decomposition cell 36 of the ultraviolet decomposition unit 31are connected together through an acid electrolytic water feed pipe 39such that the strong acid electrolytic water is sprayed into thedecomposition cells 36 by opening a valve (not shown) set up at aportion of connection between each decomposition cell 36 and the acidelectrolytic water feed pipe 39.

Furthermore, the cathode side of the electrolytic water producingapparatus 34 and each decomposition cell 36 of the ultravioletdecomposition unit 31 are connected together through an alkalielectrolytic water feed pipe 40 such that the strong alkali electrolyticwater is sprayed into the decomposition cells 36 by opening a valve (notshown) set up at a portion of connection between each decomposition cell36 and the alkali electrolytic water feed pipe 40.

The opposite ends of a circulation pipe 41 having a pump 42 areconnected to upper and lower parts of the scrubber 32, so that gashaving flowed to the lower part of the scrubber 32 through theultraviolet decomposition unit 31 is transferred to the upper part ofthe scrubber 32 for circulation in the scrubber 32 after being forcedupward through the circulation pipe 41 with the pump 42.

In addition, the scrubber 32 is equipped with a pH meter 55, so that apH value of the polluted gas having flowed into the scrubber 32 may bemeasured with the pH meter 55.

Furthermore, the circulation pipe 41 is connected to the acidelectrolytic water feed pipe 39 and the alkali electrolytic water feedpipe 40 through valves (not shown), so that the strong acid electrolyticwater and the strong alkali electrolytic water are selectively sprayedto the gas circulating in the scrubber 32 by opening the valvesaccording to the pH value of the polluted gas by measurement with the pHmeter 55, and as a result, the intermediate product contained in the gasis neutralized for decomposition.

In addition, a drainage neutralization tank 44 is installed in adrainage path 48 extending from the scrubber 32, while the acidelectrolytic water feed pipe 39 and the alkali electrolytic water feedpipe 40 are respectively connected to the drainage neutralization tank44 through valves, so that waste water reserved in the drainageneutralization tank 44 is drained to the outside after being neutralizedby adding the strong alkali electrolytic water or the strong acidelectrolytic water to the waste water.

An activated carbon filter is incorporated in the activated carbonadsorption unit 33, wherein a small quantity of compound still remainingin the gas having passed through the scrubber 32 is removed byadsorption.

In addition, an exhaust pipe 46 having a pump 45 is connected to theactivated carbon adsorption unit 33, so that clean gas having passedthrough the activated carbon filter is exhausted to the outside throughthe exhaust pipe.

The system for decomposing the gaseous organic compound is applied asfollows.

The polluted gas containing the organic compound is introduced throughthe gas inlet 37 into the ultraviolet decomposition unit 31 along itsdiameter after being drawn from the soil by suction, as shown in FIG.22. Then, the strong acid electrolytic water and/or the strong alkalielectrolytic water produced in the electrolytic water producingapparatus 34 are or is brought into touch with the introduced pollutedgas by spraying into the decomposition cells 36, while ultraviolet raysare irradiated to the polluted gas by turning on the low pressuremercury lamps 35.

In consequence, the organic compound contained in the polluted gas isdecomposed by ultraviolet irradiation, while the reaction ofdecomposition is accelerated in the presence of the strong acidelectrolytic water and/or the strong alkali electrolytic water.

An intermediate product resulting from decomposition of the organiccompound is contained in the polluted gas that is extracted through thegas outlet 38 after having passed through the ultraviolet decompositionunit 31, and hence, the polluted gas which contains the intermediateproduct flows into the scrubber 32.

The polluted gas having flowed into the scrubber 32 circulates in thescrubber 32 through the circulation pipe 41 for a certain period oftime, while the pH value of the polluted gas is measured with the pHmeter 55. Then, on the occasion of passage of the polluted gas throughthe circulation pipe 41, the strong acid electrolytic water or thestrong alkali electrolytic water is sprayed to the polluted gasaccording to the pH value measured with the pH meter 55, and as aresult, the intermediate product contained in the polluted gas isneutralized.

There are some cases where the polluted gas containing the intermediateproduct shows neutrality depending on the kind of organic compoundscontained in the polluted gas. In this case, the strong acidelectrolytic water and the strong alkali electrolytic water aresimultaneously sprayed for decomposition of the intermediate product.

In addition, a small quantity of organic compound still remaining in thegas having passed through the ultraviolet decomposition unit 31 is alsofurther decomposed by spraying of the strong acid electrolytic water orthe strong alkali electrolytic water.

A part of the intermediate product which has not decomposed or a part ofa by-product resulting from neutralization is drained to the drainagepath 43 after being dissolved in the sprayed electrolytic water.

Water drained from the scrubber 32 to the drainage path 43 assumesacidity or alkalinity in most cases, and therefore, needs to be drainedto the outside after being neutralized by adding the strong alkalielectrolytic water or the strong acid electrolytic water in the drainageneutralization tank 44.

The gas having circulated in the scrubber 32 for a certain period oftime flows into the activated carbon adsorption unit 33, and is thenexhausted to the outside after the intermediate product and the organiccompound that still remains in small quantity are removed by adsorptionwith the activated carbon filter.

Incidentally, the ultraviolet decomposition unit 31 may be also used asthe intermediate product treatment apparatus. In this case, eachdecomposition cell 36 is equipped with the pH meter 55. Thus, theintermediate product contained in the polluted gas within theultraviolet decomposition unit 31 is neutralized for decomposition byselectively spraying the strong acid electrolytic water and the strongalkali electrolytic water from the connected acid electrolytic waterfeed pipe 39 and the connected alkali electrolytic water feed pipe 40according to the pH value measured with the pH meter 55. In addition,the strong acid electrolytic water and the strong alkali electrolyticwater sprayed for neutralization are supposed to be also applied todecomposition of the organic compound contained in the polluted gas. Inthis place, the scrubber 32 may be or may not be installed on thedownstream side of the ultraviolet decomposition unit 31.

In addition, it does not matter if the strong alkali electrolytic waterand the strong acid electrolytic water are selectively sprayed into thescrubber 32 after the organic compound contained in the polluted gaswithin the ultraviolet decomposition unit 31 is decomposed by solelyultraviolet irradiation without connecting the acid electrolytic waterfeed pipe 39 and the alkali electrolytic water feed pipe 40 to theultraviolet decomposition unit 31.

A description will now be given of examples as follows.

In the system for decomposing the gaseous organic compound as shown inFIG. 20, the decomposition cell 36 whose diameter is 200 mm and lengthis 600 mm is used, and seven low pressure mercury lamps 35 were set ineach decomposition cell. Then, the polluted gas containingtrichloroethylene (hereinafter referred to as TCE) was introduced intothe ultraviolet decomposition unit 31, and the strong acid electrolyticwater with a pH value in the range of 2.1 to 2.4 was sprayed at a flowrate of 100 ml/min.

In addition, the strong alkali electrolytic water with a pH value of11.0 was sprayed at a flow rate of 1 l/min to the scrubber 32 tocirculate the polluted gas at a flow rate of 12.5 l/min.

The test 10 was conducted in the following manner: The polluted gascontaining TCE with the concentration of 50 ppm was caused to blow intothe ultraviolet decomposition unit 31 through the gas inlet 37 at a flowrate of 400 l/min, and the concentrations of TCE, hydrogen chloride,phosgene, chlorine and ozone were measured after the lapse of 10 and 30minutes at each of the following four positions; {circle around (1)} aposition immediately before the ultraviolet decomposition unit 31;{circle around (2)} a position between the ultraviolet decompositionunit 31 and the scrubber 32; {circle around (3)} a position between thescrubber 32 and the activated carbon adsorption unit 33 and {circlearound (4)} a position behind the activated carbon adsorption unit 33.FIG. 23 shows the result of measurement on these concentrations. Inaddition, FIG. 24 shows the result of measurement on the pH values inthe scrubber 32 at a point of time of start of the test and also afterthe lapse of 10 and 30 minutes.

The test 11 was conducted in the following manner: The polluted gascontaining TCE with the concentration of 100 ppm was caused to blow intothe ultraviolet decomposition unit through the gas inlet 37 at a flowrate of 400 l/min, and the concentration of TCE, hydrogen chloride,phosgene, chlorine and ozone were measured after the lapse of 10 and 30minutes at each of the above four positions {circle around (1)}, {circlearound (2)}, {circle around (3)} and {circle around (4)}, in a waysimilar to the case of the test 10, and further the pH values in thescrubber 32 at a point of time of start of the test and also after thelapse of 10 and 30 minutes were measured. FIGS. 25 and 26 show theresult of measurement on the concentration of TCE and also the result ofmeasurement on the pH value, respectively.

The tests 10 and 11 have proven that TCE contained in the polluted gasis almost decomposed by ultraviolet irradiation, and the remainingorganic compound is also decomposed to provide the extremely lowconcentration during circulation in the scrubber 32.

In addition, it has also proven that the intermediate product resultingfrom decomposition of the organic compound by ultraviolet irradiation isalmost neutralized in the scrubber 32, and the organic compound and theintermediate product that still remains in extremely small quantity inthe gas having passed through the scrubber 32 are completely removed byadsorption with the activated carbon adsorption unit 33.

Furthermore, tests 12 to 18 were conducted in the following manner: Thepolluted gas of organic compound containing hydrogen sulfide,acetaldehyde, pyridine, ammonia, trimethylamine, acetic acid ormethylmercaptan, which are regarded as seven seriously malodoroussubstances, with the concentration of 10 ppm, are blown into the gasinlet 37 at a flow rate of 400 ml/min, using the ultravioletdecomposition unit 31, and the concentrations of the organic compoundwas measured at the above four positions {circle around (1)}, {circlearound (2)}, {circle around (3)} and {circle around (4)}, in a mannersimilar to the case of test 10, and further the concentrations ofintermediate products was measured at the above three positions {circlearound (2)}, {circle around (3)} and {circle around (4)}.

More specifically, the test 12 was conducted on decomposition of thepolluted gas containing hydrogen sulfide (H₂S) to measure theconcentration of hydrogen sulfide immediately after start of the testand also after the lapse of 10, 30, 50, and 90 minutes by spraying thestrong alkali electrolytic water into the scrubber 32.

FIG. 27 shows a change of the concentration of H₂S with the passage oftime, and FIG. 28 shows a change of the concentrations of SO₂ and ozone,which are produced as the intermediate product, with the passage oftime.

The test 13 was conducted to measure the concentration of acetaldehyde(CH₃COH) immediately after start of the test and also after the lapse of10, 30 and 50 minutes by causing the polluted gas containingacetaldehyde to blow into the ultraviolet decomposition unit through thegas inlet, while spraying the strong acid electrolytic water into thescrubber 32. FIG. 29 shows the concentration of acetaldehyde, and FIG.30 shows the concentrations of acetic acid (CH₃COOH) and ozone, whichare supposed to be the expectable intermediate product. Incidentally,though it is expected that acetic acid be produced as the intermediateproduct, actually the polluted gas having passed through the ultravioletdecomposition unit 31 contains almost no acetic acid as is apparent fromFIG. 30, so that it is supposed that there is no need to takedecomposition of acetic acid by neutralization into consideration.

The test 14 was conducted to measure the concentration of pyrridine(C₅H₅N) immediately after start of the test and also after the lapse of10, 30 and 50 minutes by causing the polluted gas containing pyridine toblow into the ultraviolet decomposition unit through the gas inlet 37,while spraying the strong acid electrolytic water into the scrubber 32.FIG. 31 shows the concentration of pyridine, and FIG. 32 shows theconcentrations of NOx and ozone, which are supposed to be the expectableintermediate product.

The test 15 was conducted to measure the concentration of ammonia (NH₃)immediately after start of the test and also after the lapse of 10, 30and 50 minutes by causing the polluted gas containing ammonia to blowinto the ultraviolet decomposition unit through the gas inlet 37, whilespraying the strong acid electrolytic water into the scrubber 32. FIG.33 shows the concentration of ammonia, and FIG. 34 shows theconcentrations of NOx and ozone, which are supposed to be the expectableintermediate product.

The test 16 was conducted to measure the concentration of trimethylamine((CH₃)₃N) immediately after start of the test and also after the lapseof 10, 30 and 50 minutes by causing the polluted gas containingtrimethylamine to blow into the ultraviolet decomposition unit throughthe gas inlet, while spraying the strong acid electrolytic water intothe scrubber 32. FIG. 35 shows the concentration of trimethylamine, andFIG. 36 shows the concentrations of NOx and ozone, which are supposed tobe the expectable intermediate product. Incidentally, though it isexpected that ammonia be produced as the intermediate product, theconcentration of ammonia could not measured because of a difficulty inmaking discrimination between ammonia and trimetylamine.

In addition, in the tests 14 to 16, though it is expected that NOx beproduced as the intermediate product, actually the polluted gas havingpassed through the ultraviolet decomposition unit 31 contains almost noNOx, so that it is supposed that there is no need to take decompositionof NOx by neutralization into consideration.

The test 17 was conducted to measure the concentration of acetic acid(CH₃COOH) immediately after start of the test and also after the lapseof 10, 30 and 50 minutes by introducing the polluted gas containing theacetic acid into the ultraviolet decomposition unit through the gasinlet.37, while spraying the strong alkali electrolytic water into thescrubber 32. FIG. 37 shows the concentration of acetic acid, and FIG. 38shows the concentration of ozone produced as the intermediate product.

The test 18 was conducted to measure the concentration ofmethylmercaptan (CH₃SH) immediately after start of the test and alsoafter the lapse of 10, 30 and 50 minutes by introducing the polluted gascontaining the methylmercaptan into the ultraviolet decomposition unitthrough the gas inlet 37, while spraying the strong alkali electrolyticwater into the scrubber 32. FIG. 39 shows the concentration ofmethylmercaptan, and FIG. 40 shows the concentration of SO₂, H₂S andozone, which are supposed to be the expectable intermediate product.Incidentally, even in this test 18, no H₂S, which was supposed to be theexpectable intermediate product, was detected from the gas having passedthrough the ultraviolet decomposition unit 31.

The tests 12 to 18 have proven that almost all the malodorous substancesmay also be decomposed by the decomposing system according to thepresent invention.

The test 19 was conducted using a test apparatus composed of a test cell49 with a capacity of 180 l that is installed on the downstream side ofa gas mixing tank 47 and is equipped with ten ultraviolet lamps 48 hungdown from the upper surface of the test cell, and VOC monitors 50respectively installed on the upstream and downstream sides of the testcell 49. With this test apparatus, ultraviolet effects on decompositionof the organic compound was examined by continuously feeding to the testapparatus the polluted gas containing TCE with the concentration of 50ppm at a flow rate of 100 l/min, 200 l/min, 300 l/min and 400 l/min.

Then, FIG. 42 shows the result of measurement on the concentration ofTCE on the upstream and downstream sides of a ultraviolet decompositionunit 2′ according to a pattern 1 where ten ultraviolet lamps 48 werelighted, a pattern 2 where seven ultraviolet lamps 48 were lighted, apattern 3 where six ultraviolet lamps 48 were lighted, a pattern 4 wherethree ultraviolet lamps 48 were lighted and a pattern 5 where oneultraviolet lamp 48 was lighted. FIG. 43 shows the decomposition rate ofTCE obtained by the expression of (1−downstream concentration/upstreamconcentration)×100%.

The test 20 was conducted in the same manner as the test 19, except thattetrachloroethylene (hereinafter referred to as PCE) was used, insteadof TCE. FIG. 44 shows the result of measurement on the concentration ofPCE, and FIG. 45 shows the decomposition rate of PCE.

The test 21 was conducted in the same manner as the test 19, except thatcis-1,2-dichloroethylene (hereinafter referred to as cis-1,2-DCE) wasused, instead of TCE. FIG. 46 shows the result of measurement on theconcentration of cis-1,2-DCE, and FIG. 47 shows the decomposition rateof cis-1,2-DCE.

In addition, the test 22 was conducted in the same manner as the test19, except that monochlorobenzene was used, instead of TCE. FIG. 48shows the result of measurement on the concentration ofmonochlorobenzene, and FIG. 49 shows the decomposition rate ofmonochlorobenzene.

The test 23 was conducted in the same manner as the test 19, except thatethyl acetate was used, instead of TCE. FIG. 50 shows the result ofmeasurement on the concentration of ethyl acetate, and FIG. 51 shows thedecomposition rate of ethyl acetate.

The test 24 was conducted to measure the concentration of toluene byfeeding gas containing toluene, instead of TCE, with the concentrationof 50 ppm at a flow rate of 100 l/min to a test apparatus similar tothat used for the test 19. FIG. 52 shows the result of measurement onthe concentration of toluene.

The tests 19 to 24 have proven that the ultraviolet decomposition rateis increased with the decreases of flow rate of the test samples, andtetrachloroethylene having a large number of chlorine atoms is morelikely to be decomposed by ultraviolet irradiation, whereas ethylacetate and toluene that contain no chlorine are hardly to be decomposedby ultraviolet irradiation.

The test 25 was conducted to examine the effects on acceleration ofdecomposition in a case of spraying the strong alkali electrolyticwater, the strong acid electrolytic water and a mixture thereof beforeultraviolet irradiation. For the test 25, an ultraviolet lamp 48 forirradiation of ultraviolet rays whose wavelength is 254 nm at output of30 W was installed in the test cell 49 whose inner diameter is 120 mmand height is 1300 mm, as shown in FIG. 53, and a mixture of TCE gaswith diluting air was introduced into a test cell 49 at a flow rate of 3l/min. Then, spraying either the strong acid electrolytic water, thestrong alkali electrolytic water, a mixture of strong acid electrolyticwater and strong alkali electrolytic water at the ratio of 1 to 1 andtap water into the test cell 49 at a flow rate of 10 l/min using anatomizer 51, and then repeatedly turning on and off the ultraviolet lamp48 after stabilization of the concentration of TCE, the test 25 wasconducted to measure the concentration of TCE in the gas extracted fromthe test cell through an extraction port 52 formed in a portion on thedownstream side of the test cell at an interval of 10 minutes. FIG. 54shows the result of measurement on the concentration of TCE, togetherwith the decomposition rate of TCE.

The test 25 has proven that use of the strong acid electrolytic water,the strong alkali electrolytic water and the mixture of strong acidelectrolytic water and strong alkali electrolytic water for sprayingapparently increases the decomposition performance more than that in thecase where tap water is sprayed.

FIGS. 55 and 56 show a test apparatus used for the test 26. The testapparatus used herein has a test cell 49 having an exchangeableultraviolet lamp 48 hung down from an upper surface of the test cell 49.In a lower part of the peripheral wall of the test cell 49, there are afirst gas inlet 37 a for introducing gas along a diameter, and a secondgas inlet 37 b for introducing gas along a tangent line. In an upperpart of the peripheral wall of the test cell 49, there are a first gasoutlet 38 a for extracting gas along a diameter and a second gas outlet38 b for extracting gas along a tangent line.

Then, using the ultraviolet lamp 48 with a protection tube whichirradiates ultraviolet rays of 185 nm wavelength and also ultravioletrays of 254 nm wavelength at output of 13 W, or alternatively, using theultraviolet lamp 48 without a protection tube which irradiatesultraviolet rays of 185 nm wavelength and also ultraviolet rays of 254nm wavelength at output of 40 W, the test 26 was conducted to measurethe concentration of TCE on the upstream and downstream sides of thetest cell 49 and to find the decomposition rate of TCE for one casewhere gas containing TCE with the concentration of 50 ppm was caused toflow at a flow rate of 100 l/min, 200 l/min, 300 l/min and 400 l/minthrough a flow path {circle around (1)} extending from the first gasinlet 37 a to the first gas outlet 38 a and for another case where thegas was caused to flow through a flow path {circle around (2)} extendingfrom the second gas inlet 37 b to the second gas outlet 38 b. FIG. 57shows the result of the test 26.

The test 26 has proven that introduction of the polluted gas into thecell along the diameter thereof toward the cross sectional centerprovides the decomposition performance higher than that in case ofintroducing the polluted gas in the tangential direction.

The reason is because introduction of the gas in the tangentialdirection of the cell causes a flow of the gas along the wall surface ofthe cell, so that the ultraviolet intensity is decreased, while the timethe gas stays in the cell is reduced.

FIG. 58 shows a test apparatus used for tests 27 to 29. The testapparatus used herein has a test gas-loaded Tedlar bag 53 connected to atest cell 49 whose inner diameter is 45 mm, length is 500 mm andcapacity is 800 ml, and in which the ultraviolet lamp 48 is housed.Then, gas was introduced into the test cell 49 by suction with a pump 54until the concentration of the gas reaches a certain value. Then, thetests were conducted to observe a change of the concentration of gasusing a VOC sensor 50 by lighting the ultraviolet lamp 48 for 20minutes.

The tests were conducted for one case where the initial concentration ofgas was 10 ppm and also for another case where the initial concentrationof gas was 100 ppm, by using GLS6UN (manufactured by TOSHIBA INC) forirradiation of ultraviolet rays whose wavelength is 185 nm and thosewhose wavelength is 254 nm, GLS6UJ (manufactured by TOSHIBA INC) forirradiation of ultraviolet rays whose wavelength is 254 nm and BlackLight (manufactured by MIYATA ELEVAM INC) for irradiation of ultravioletrays whose wavelength is not less than 300 nm as the ultraviolet lamp48.

More specifically, the test 27 was conducted using trichlorotethylene asthe test gas. FIG. 59A shows the concentration of TCE for the case wherethe initial concentration of gas was 10 ppm, and FIG. 59B shows theconcentration of TCE for the case where the initial concentration of gaswas 100 ppm.

The test 28 was conducted using tetrachloroethylene as the test gas.FIG. 60A shows the concentration of PCE for the case where the initialconcentration of gas was 10 ppm, and FIG. 60B shows the concentration ofPCE for the case where the initial concentration of gas was 100 ppm.

The test 29 was conducted using cis-1,2 dichloroethylene as the testgas. FIG. 61A shows the concentration of cis-1,2-DCE for the case wherethe initial concentration of gas was 10 ppm, and FIG. 61B shows theconcentration of cis-1,2-DCE for the case where the initialconcentration of gas was 100 ppm.

The tests 27 to 29 have proven that use of the ultraviolet rays whosewavelength is not less than 300 nm causes only a change of concentrationto a value almost as much as a measured value of the blank, resulting inno decomposition of the organic compound.

The test 30 was conducted to verify the possibility of the ultravioleteffects on decomposition of yperite ((ClCH₂CH)₂S) used as toxic gas forchemical weapon. For the test 30, an ultraviolet lamp for irradiation ofultraviolet rays whose wavelength is 185 nm and those whose wavelengthis 254 nm was installed in a Duran bottle of 500 ml, and a Tedlar bagcontaining chloromethylmethylsulfide (ClCH₂SCH₃, which will behereinafter referred to as CMMS) as a yperite pseudo agent was connectedto the Duran bottle to replace air within the Duran bottle with CMMS bysuction with a pump separately connected to the Duran bottle.

Thereafter, the ultraviolet lamp was turned on, and then theconcentration of CMMS was measured. FIG. 62 shows the result ofmeasurement on the concentration of CMMS.

The test 30 has proven that the yperite pseudo agent is also decomposedas much as half by ultraviolet irradiation, although the decompositionspeed is supposed to be not so high.

1. A system for decomposing an organic compound, comprising: aultraviolet decomposition unit for decomposing an organic compoundcontained in polluted liquid by irradiating ultraviolet rays whosewavelength is less than 300 nm to the polluted liquid containing saidorganic compound; and an intermediate product treatment apparatus,connected to an acid electrolytic water feed pipe and an alkalielectrolytic water feed pipe through valves, to neutralize anintermediate product, which results from decomposition of said organiccompound, for decomposition by selectively adding strong alkalielectrolytic water and strong acid electrolytic water to the pollutedliquid containing said intermediate product.
 2. The system fordecomposing the organic compound according to claim 1, wherein saidintermediate product treatment apparatus is connected to the downstreamside of said ultraviolet decomposition unit to selectively add thestrong alkali electrolytic water and the strong acid electrolytic waterto the polluted liquid having passed through said ultravioletdecomposition unit.
 3. The system for decomposing the organic compoundaccording to claim 1, wherein said intermediate product treatmentapparatus is installed at an intermediate part of said ultravioletdecomposition unit to selectively add the strong alkali electrolyticwater and the strong acid electrolytic water to the polluted liquidwithin said ultraviolet decomposition unit.
 4. The system fordecomposing the organic compound according to claim 1, wherein thestrong alkali electrolytic water and/or the strong acid electrolyticwater are or is added to said polluted liquid on the upstream side ofsaid ultraviolet decomposition unit.
 5. The system for decomposing theorganic compound according to claim 1, wherein said ultravioletdecomposition unit is made up of a reaction vessel composed of aplurality of ultraviolet lamps set up around a transparent tube thatallows the polluted liquid to pass and reflectors respectively arrangedbehind said ultraviolet lamps.
 6. The system for decomposing the organiccompound according to claim 5, wherein said reaction vessel includes aplurality of reaction vessels connected in series.
 7. The system fordecomposing the organic compound according to claim 5, wherein saidreaction vessel includes a plurality of reaction vessels connected inparallel.
 8. The system for decomposing the organic compound accordingto claim 5, wherein said transparent tube is made of a material such assynthetic quartz glass that permits transmission of 80% or more ofultraviolet rays whose wavelength is not less than 172 nm. 9-15.(canceled)